The Only Duo That Survived - 30 Years of the Pet Shop Boys

One of Britain's oldest bands, the Pet Shop Boys, are poised to have their first number one album in almost 20 years. They will find out on Sunday if they have nudged Robin Thicke off the top spot (they're currently at number two, and only a 1,000 sales separate the acts). It's a remarkable achievement for a band which has been together for 32 years.

The success of the Pet Shop Boys is extraordinary - 70million albums sold worldwide; 40 singles in the UK Top 20; global tours every year that take in Russia, the Far East and South America. The Guinness Book of Records notes that they are the fourth biggest dance act in the world - trailing only Madonna, Michael Jackson and Donna Summer. What's more intriguing than the success, however, is the fact that they have managed to stay together. The success doesn't require scrutiny - a fusion of insistent, vivacious melodies, intelligent lyrics and clever chord progressions: the essence of electronic pop.

The survival of the partnership is more intriguing. Historically, of course, these marriages don't last. Close as twins, duos burn out in the heat and intensity of the relationship. It's inevitable. Everything becomes airless, claustrophobic. It's like watching the surge and dissolution of a chemical combustion. "The time for putting an end to our collaboration has arrived," wrote Gilbert to Sullivan in 1890, after the feuding became intolerable. The Everly Brothers famously didn't speak for a decade. Simon and Garfunkel still prowl warily round each other. And that's the typical pattern. But Tennant and Lowe seem more cordial than ever. How come?

Many years ago I was involved in a TV show in which they appeared, where the songs of Elvis Presley were covered by modern pop stars. The abiding memory is their disjuncture. They clearly liked one another, joked together, lunched with each other, but in the end, their lives and interests were separate. Aside from work, and an interest in art, they had nothing in common. Tennant is scholastic and dry - his demesne is a cottage in Durham, surrounded by books and a dog called Kevin - Chris Lowe is the all-night party animal, the football fanatic. His closest friend was the late Dainton Connell, "the bear" of Arsenal's Highbury terraces.

This sense of remove is apparent in their public faces. They are like two indifferent brothers bound only by blood. It is impossible to find photographs of them in which either notes the presence of the other. Usually they are just staring out at the world, quizzically. On stage, too, they look as if they have been caught together by chance. In their fifty or so music videos, there is only one shot of them actually interacting (a shared laugh, captured in Being Boring). Even when they made a full-length feature film, the disastrous It Couldn't Happen Here, they spoke only a few lines to each other.

But the distance is its own reward. No contempt is bred by intimacy. They're too foreign to get on each other's nerves. There are no rows. It also means that they both adhere to the rigidly defined roles necessary to make the machinery of the whole thing work (in the video for Somewhere, Tennant is organising the lights and sets while Lowe attends to the music, naps and eats sandwiches).

And there remains another secret to the union. Jealousy is the cancer that ultimately kills all duos: stored up grievances over uncredited melodies, quiet fury over string arrangements that were excised to make way for the other's horn section. On and on. Each imagines he is the key to success and the other is merely the passenger. "You'd be a gas station attendant without me," shrieked one of the Louvin brothers to his sibling. "Simon and Garfunkel were a team," said Art, in 2007. "I always knew that but I'm not so sure Paul did."

In the case of Tennant and Lowe, however, the reverse is true. This is not a verdict they would recognise but it leaks out in interviews. "I wouldn't have the confidence to go solo," Tennant said. He described how their first manager, Tom Watkins, tried to get rid of Lowe "because he obviously didn't do anything." Tennant saw Watkins off: "I'm clever but Chris is a genius." Lowe, meanwhile, appears to imagine it's the other way round. He's the former architecture student who had no ambitions to become a pop star until he met Tennant in a record shop.

Whatever he's brought to the table, it's Tennant who has provided the choirboy mewling and the wry irony that have become the distinguishing characteristics of the group. "Being famous," he said, "is something that only happens to other people." The truth of course is that neither could have succeeded without the other. Tennant is chords and lyrics; Lowe is melodies and basslines. They fill each other's gaps. The endearing lack of ego, however, has helped them to become the longest surviving and most successful duo in the history of music.